1. Field of the Invention
The present invention relates to a novel gas turbine rotor blade which is used in a turbine for converting kinetic energy produced with expansion of a combustion gas to rotational motive power. The present invention also relates to a gas turbine using the rotor blade, and a power plant using the gas turbine.
2. Description of the Related Art
FIG. 12 is a sectional view showing a general structure of a gas turbine. The gas turbine mainly comprises a compressor 1, a combustor 2, and a turbine 3. The compressor 1 performs adiabatic compression by using, as a working fluid, air sucked from the atmosphere. In the combustor 2, fuel is mixed in the compressed air supplied from the compressor 1, and the mixture is burnt to produce a high-temperature and high-pressure gas. The turbine 3 generates rotational motive power when the combustion gas introduced from the combustor 2 is expanded. Exhaust from the turbine 3 is released to the atmosphere. Motive power left after subtracting the motive power required to drive the compressor 1 from the rotational motive power generated by the turbine 3 is obtained as effective motive power generated by the gas turbine, which is available to drive a generator.
As shown in FIG. 12, the turbine 3 comprises a turbine rotor blade 4, a turbine stator blade 5 for rectifying gas flows in an expansion process of the combustion gas, and a turbine rotor 6 having an outer periphery to which is fixed the turbine rotor blade 4.
FIGS. 13A and 13B are each a perspective view showing a shroud cover of the known turbine rotor blade. An outer surface of the turbine rotor blade 4 is heated to high temperature because the turbine rotor blade is used to convert kinetic energy produced with expansion of the combustion gas to rotational motive power. As shown in FIGS. 13A and 13B, a shroud cover 7 is provided to prevent the combustion gas from leaking toward the outer peripheral side and is fitted with the adjacent turbine rotor blades 4 to suppress vibrations.
Patent Document 1 (JP,A 2000-291405) discloses a shroud cover in which, for the purpose of cooling the whole of the shroud cover, a plenum is formed such that the interior of a blade section is also communicated with inner cooling holes through the plenum. A plurality of discharge holes are extended from the plenum and are opened at peripheries of the shroud cover. A possibility of creep rupture is reduced by cooling the shroud cover with such an arrangement.
Further, Patent Document 2 (JP,A 11-500507) discloses a shroud cover in which two shroud cooling air holes are formed to cool the shroud cover. This related art is also intended to reduce a possibility of creep rupture by cooling the shroud cover.